1. Field of the Invention
This invention relates to a process for forming a foamed product, e.g., a cushion for a seat cushion of a vehicle seat, a cushion for a seat back of the vehicle seat and the like, in which a cushioned padding formed of foamed resins is integrated with a trim cover.
2. Description of the Prior Art
In general, a foamed product integral with a sheet of covering material is made by causing a three dimensional trim cover to be supported on a lower die, causing an upper die to be combined with the lower die in such a manner to clamp the upper die against the lower die, pouring expandable resins into a forming cavity within the lower die through a pouring hole of the upper die, and causing the expandable resins to foam in the forming cavity, to thereby produce a cushioned padding made of the foamed resins and integrated with the trim cover.
Another method for forming a foamed product integral with a sheet of covering material is performed utilizing an apparatus which comprises an outer frame die, a vacuum applying box housed within the outer frame die, a supporting die arranged on the vacuum applying box and having air-ventilating holes, and an upper die having a pouring hole for allowing expandable resins to be poured into a forming cavity within the outer frame die therethrough. The vacuum applying box is coupled to air-absorbing means for applying suction or vacuum to the vacuum applying box. When a trim cover is put on the supporting die, suction or vacuum from the air-absorbing means is applied to the vacuum applying box and then applied to the trim cover put on the supporting die through the air-ventilating holes of the supporting die, resulting in the trim cover being drawn onto the supporting die and being positively set on the supporting die.
In order to form a foamed product integral with a sheet of covering material, which has a good touch and ensures a comfortable sitting feeling, an air-permeable, three dimensional trim cover which has a two-layer structure comprising a layer of foamed material and a sheet of covering material laminated with the foamed material layer is employed.
In a condition where the air-permeable trim cover is placed on the trim cover supporting die and is drawn onto the supporting die by the applying of vacuum to the trim cover put on the supporting die, when expandable resins are poured into the forming cavity within the outer frame die and then start to foaming, gas is generated due to the foaming of the expandable resins and pressure within the forming cavity is then increased by the gas and becomes higher than a pressure within the outer frame die. As a result, the foamed resins are excessively impregnated into the foamed material layer of the trim cover.
In order to prevent the foamed resins from being excessively impregnated into the foamed material layer of the trim cover, there is proposed a trim cover which has a thin layer of skin applied onto a foamed material layer of the trim cover (Japanese Utility Model Publication No. Hei. 5-44099).
However, even if the trim cover having the thin layer applied onto the foamed material layer is employed and a cushion for a seat is made as a foamed product by the above forming apparatus, foamed resins within the forming cavity of the apparatus are excessively impregnated into the foamed material layer, resulting in the foamed product having a poor touch and a poor sitting feeling.